Power Packs are a compilation of some of our best and most popular articles. They focus on a specific topic, bringing you a handy mix of tips, techniques, and how-to answers. They are packaged as a free ePub and .pdf file download. Why ePub? These files are compatible with most mobile tablets and smartphones, plus they tend to fit right into your eBook libraries—giving you on-the-go access any time you want. Why .pdf? While .pdfs aren't so handy on small screens, the ease of use on PCs and Macs is excellent.